The Future of Sustainable Aquaculture

Atlas of The Future’s Aquapod stationed in Mexico’s Sea of Cortez

Florinda Cardoso- Natural Resources Conservation

Lauren Moura- Animal Science

Louie Huang- Building Construction Technology

Trevor Mackowiak- Environmental Sciences


From grilling it at home to ordering a fancy sushi platter, seafood is a versatile and staple protein for many diets around the world and is growing in demand as the world’s population increases. As demand increases, commercial fisheries become more industrialized, and the industry is heavily reliant on artificial aquaculture systems to raise fish such as salmon. History has shown us time and time again that industrialization often comes at the cost of our ecosystems. We do not want history to repeat itself as we tackle the issue of feeding our growing population. However, in its current state of onshore, shallow water fisheries, salmon aquaculture may be leading environmental degradation.

We all know that animals produce waste, and dealing with said waste is an integral part to any form agriculture. The same applies to the salmon raised in aquaculture operations. The waste they produce, known as effluent waste, is a combination of fecal matter and excess feed, which eventually settles on the floor causing sediment enrichment of carbon and nitrogen (Holmer et al., 2005, p. 183). Ecosystems usually have the natural ability to recycle these nutrients out of the sediment and disperse it back into the surrounding environment, though this process only works up to a certain capacity. If the rate of nutrient addition is greater than recycling in the ecosystem, the nutrients accumulate and result in negative impacts. (Holmer et al., 2005, p. 194). This affects us by contaminating our shores where we indulge in recreational activities such as fishing, enjoying the beach, etc., resulting in areas on shore being closed off from public use.

Current aquaculture systems in the United States are typically found near shore. Salmon farmers house their fish in pens that float on the surface of the water. These pens can be 90 feet across and 60 feet deep, and they can hold tens of thousands of salmon which clearly produce a lot of waste (Foley). The large volume of these near shore pens contribute to the sediment enrichment issue. With the pens reaching a depth of 60 feet, the bottom of the pens are close to the floor of the shallow waterways in which they are located. With such minimal distance between the pen and the floor of the waterway, there is little water flow to carry waste away from the vicinity and it all settles within a short distance of the pen. Over time the waste accumulates to unsustainable quantities.

The degree of pollution can be measured by total nitrogen (TN) and total organic carbon (TOC). Elevated levels of TOC and TN indicate that the body of water in question is polluted by effluent waste (Whitehead, 2018). Bannister et al. (2014) measured the TOC levels in the sediments immediately below salmon cages at near shore facilities, compared with the levels at reference locations. They concluded that TOC levels were 50% higher in the sediment at the farming locations than they were at the reference sites (Bannister et al., 2014, p. 41). The study concluded that sediment in the immediate vicinity of the cages was significantly more polluted than the sediment at the reference locations (Bannister et al. 2014).

The biggest impact that effluent waste from salmon farms has on sediment composition stems from the process of eutrophication, which has negative effects on aquatic wildlife and vegetation. Eutrophication is when a body of water receives an excess of nutrients typically from residential life, urban runoff, or agricultural practices like aquaculture operations (Bowman et al., 2017, p.  249). The excess nutrients disposed into the water from salmon aquaculture systems benefit some primary producers, allowing them to reproduce at a high volume which cause algae blooms. That said, this abnormal volume of algae is not sustainable, and the algae will eventually die. Bacteria feed on this dead organic matter and use dissolved oxygen to do so. Since there is a lot of dead algae, bacteria will feed rapidly while simultaneously using up dissolved oxygen in the water.  The decrease of dissolved oxygen leads to the death of many other aquatic organisms in the area. This change in abundance of primary producers negatively influences species higher up the food chain which will result in a decrease in populations of vegetation and various fish species (NOAA, 2018).

Eutrophication is triggered if the TN concentration of the waterway exceeds 0.80mg/L (Xu et al., 2015, p. 1051). The Changshou Reservoir in China experienced a high level of eutrophication and Sheng et al. (2006) concluded that it was due to the reservoir’s above average density of salmon aquaculture operations. They measured the concentration of TN in the reservoir during the month of October from 1999 to 2001 and found the average level it to be 2.32mg/L (Zhang et al., 2006, p. 93). This level of pollution exceeds the capabilities of the ecosystem to recycle these nutrients, and eutrophication became increasingly likely.

While eutrophication may seem like soley an environmental issue, it has the potential to cause major economic losses. Eutrophication causes fish kills, which can decrease the fish stock significantly or, in the most extreme cases, removes them from ecosystem entirely. Such an event happened in Hong Kong in 1998. Eutrophication wiped out 90 percent of the entire stock of Hong Kong’s fish farms and resulted in an estimated economic loss of $40 million USD (Eutrophication and Hypoxia Impacts). Similarly, in the 1980’s the Black Sea ecosystem was in decline due to eutrophication. The increase in nutrients combined with fairly shallow water lead to massive fish kills. This left the ecosystem susceptible to disturbances which ultimately lead to extensive losses in Turkish fishing industries (Bowman et al., 2017, p. 250). In order to protect the economic performance of nations which rely on aquaculture, eutrophication must be kept to a minimum.

If aquaculture farms are planned with the recycling capacity of the ecosystem in mind, nutrient enrichment can be greatly diminished. While conventional aquaculture practices produces waste that results in nutrient enrichment of sediment (Carroll et al., 2003, p. 173), an emerging practice known as offshore aquaculture could be the solution. Offshore aquaculture is the practice by which cages made up of nets are placed 3-200 miles offshore (NOAA, 2016) in depths ranging from 82ft-328ft (Kapetsky, Aguilar-Manjarrez, & Jeness, 2013, p. 3). As depth of the waterway increases, the rate of the current does as well. As the rate of the current increases, there is greater dispersion of organic nutrients (Gentry et al., 2016). Carroll et al. (2003) recorded the current speeds at varying depths of salmon farms and found that at depths of less than 82ft the current speed was less than 1.2in/s, depths between 82ft and 164ft the current speed was 1.6in/s-2.4in/s, at depths between 164ft and 246ft the current speed was 2.8in/s-3.9in/s, at depths of greater than 246ft the current speed was 3.9in/s-9.8in/s. They measured the TOC at the varying classes and found that the higher the depth and current speed the lower the TOC. For example, salmon farms at depths less than 82ft had TOC levels between 34mg/g and 41mg/g, while farms at depths greater than 246ft had TOC levels of less than 20mg/g (Carroll et al., 2003, p. 169). By planning the facilities offshore, and therefore at greater depths, water currents around the facilities are much greater than when compared to inshore farms . This allows the settling of effluent waste to spread out over a larger area, thus keeping the sediment composition directly below the farms from becoming heavily polluted (Gentry et al., 2016, Carroll et al. 2003). By increasing the dispersal range of effluent waste, biological life around the farms are better able to naturally recycle the nutrients. With less polluted waters and adequate dissolved oxygen, all fish are able to live healthier lives.

In order to raise fish in open waters, designers have to make a cage that is able to withstand the force of open ocean waves (Arnold, 2006). Companies like InnovaSea have achieved this and already began capitalizing on the offshore structures, their SeaStation and Aquapod (Innovasea, n.d) offer two options for aquaculture farmers. The Aquapod is a spherical arrangement of triangular net panels fastened together that allows the pod to withstand a variety of conditions and hold a diversity of species (Innovasea, n.d).  This fish farm pod looks like something out of a sci-fi movie, whereas the SeaStation appears to be a more conventional and cost effective solution. China recently constructed a farm similar to InnovaSea’s SeaStation, the structure is 125 feet high, holds 1.76 million cubic feet of volume, and can generate 1,500 tonnes of salmon per season (every 2 years) (Tang, 2018). The cage is planned to be installed in the Yellow Sea, 130 nautical miles east of Rizhao (Tang, 2018) and the depth can be adjusted from 13-164 feet accordingly to optimal temperature conditions for the salmon and effluent waste dispersal (Tang, 2018). Estimates show that offshore aquaculture in the Yellow Sea will support a $15.7 billion industry (Tang, 2018) and will ease pressures on near shore farming (Tang, 2018).

The United States was ranked number 1 in global offshore aquaculture development potential by the Food and Agriculture Organization for The United Nations (Kapetsky, Aguilar-Manjarrez, & Jeness, 2013, p. 26) The ranking is on the basis of ocean areas encompassing 2-300 miles away from the shoreline of the country’s land masses with suitable depths, current speeds, and cost effectiveness based on travel time and accessibility (Kapetsky, Aguilar-Manjarrez, & Jeness, 2013, p. xv). We urge that the United States develops a process for developing offshore aquaculture in our homewaters. Failure to set up the proper framework for offshore aquaculture development will result in loss of a massive economic opportunity, damage to the environment, and a higher potential for unregulated seafood. Allowing effluent waste to disperse in offshore waters will spread the waste in a greater area rather than it being condensed onshore. You may now be thinking of the popular propaganda slogan from the 1970’s, “the solution to pollution is dilution.” In many cases this slogan is inaccurate but in this case it can be taken with a grain of salt. With the waste from salmon aquaculture systems spread over a greater area, a greater amount of biological life is able to naturally recycle the contaminants out of the water system.

In 2015 the average United States citizen ate 15.5 pounds of fish (Gewin, 2017) and in 2016 the United States imported more than 2.5 million tons of edible fish (Lester et al., 2019) that amounts to 90% of the market value, half of that coming from aquaculture in other countries (Lester et al., 2018). The U.S. exports half of its wild caught seafood (Knapp & Rubino, 2016, p. 214) though even if it did not export, the supply would be insufficient for the domestic market (Knapp & Rubino, 2016, p. 214). The United States fish consumption has gone up while its amount of catch has remained the same (Gewin, 2017) this has become a global trend. The World Bank predicts that by 2030, two-thirds of fish eaten will have come from aquaculture (GreenBiz).  The United States is home to the highest area of cost effective land for offshore aquaculture (Kapetsky, Aguilar-Manjarerez, & Jeness, 2013, p. 26) when compared on a global scale and should seek to use it to its advantage.

To ensure the development of American aquaculture movement is sustainable, streamlining of the regulatory process for establishing deepwater aquaculture operations must be prioritized. This makes it easier for businesses to establish these farms from the beginning. Offshore aquaculture operates 3-200 miles offshore (NOAA, 2016) while the federal Exclusive Economic Zone encompasses 3-200 miles offshore (Lapointe, 2013, p. 1), this means that offshore operations occur in federal waters, here is where things become cloudy as to who is responsible for regulating offshore aquaculture.

In order to allow the development of offshore aquaculture in the United States to create a sustainable source of food, the permitting process has to be streamlined to allow easy entrance into the market. There have been previous attempts to streamline the process, the National Offshore Aquaculture Acts of 2005 and 2007 which both failed to pass in congress (Lester et al., 2018). These acts granted the Secretary of Commerce the right to establish a permitting process for the development of offshore aquaculture in the U.S. waters (Congress, 2007). Due to this the current process for entering the offshore aquaculture is unclear and unstable, which scares investors away from what could possibly be an incredible investment. The federal government allocated NOAA permission to grant permits for up to 20 offshore aquaculture farms in the Gulf of Mexico (Gewin, 2018) in January of 2016. Though in 2018 the permits were ruled unlawful in court because they go beyond NOAA’s legal reach (Center for Food Safety, 2018).  When writing the permitting application, NOAA described the offshore aquaculture farms as fishing, which is their responsibility, though plaintiffs argued that aquaculture is more farming than fishing (Center for Food Safety, 2018). These court results promulgated that under current federal law, the development of offshore aquaculture in the United States is not permitted (IntraFish Media, 2018). This means a new regulatory process is imperative to allow potential offshore aquaculture farmers to develop their farms in the United States’ waters.

There are three government agencies involved in the offshore permitting process (Gewin 2017), including the National Oceanic and Atmospheric Administration (NOAA) (NOAA, 2017), U.S. Army Corps of Engineers (USACE), and the U.S. Environmental Protection Agency (EPA) (NOAA, 2017). NOAA has assumed the role of permitting any offshore aquaculture farm, currently in The Gulf of Mexico. In 2016 NOAA was alloted to permit 20 offshore aquaculture operations (NOAA, 2018), though in 2018 the permits were repealed before even being distributed (IntraFish Media, 2018). The USACE grants permits that protect the navigable waters of the U.S. (NOAA, 2017) while the EPA is totally different, they permit the discharge of pollution from an offshore aquaculture operation (NOAA, 2017). A potential offshore aquafarm might meet the USACE and EPA qualifications, though it is still not allowed to start its operations until NOAA receives approval to distribute permits.

There are also four government agencies involved with the authorization of offshore aquaculture operations. This includes the Bureau of Ocean Management (BOEM), the Bureau of Safety and Environmental Enforcement (BSEE), the U.S. Coast Guard (USCG), and the U.S. Fish and Wildlife Service (USFWS) (BOEM, 2017).

One alternative for offshore aquaculture is to repurpose old fossil fuel rigs which provide the benefits of: the availability of large volumes of good-quality water, reduced user conflicts, increased employment, and decreased reliance on foreign imports (BOEM, 2007), but require cooperation from all four agencies. The BOEM authorizes the right to use for offshore operations that use an existing federal outer continental shelf facility (NOAA, 2017). The BSEE authorizes proposed activities that convert oil and gas facilities to a new purpose (NOAA, 2017). BSEE started an initiative in the mid 1980’s called the Rigs to Reef program to repurpose old fossil fuel rigs and can be used to promote offshore aquaculture (Rigs to Reef, n.d). While the U.S. Coast Guard authorizes that the proposed facilities will have the correct lights and signals that allow for safe maritime navigation (NOAA, 2017). The U.S. Fish and Wildlife Service authorizes that proposed actions are in compliance with all fish and wildlife laws including The Fish and Wildlife Conservation Act and the Endangered Species Act (NOAA, 2017). The difficult part for the company is that every agency has different permit applications and periods. Companies could possibly receive approval from one agency, but get denied by another for a specification, extending the permitting process and making it complicated.

The proposed offshore aquaculture policy is a win-win in the political system, the Trump administration has already expressed in favor of expanding aquaculture in America (Gewin, 2017). Not only is offshore aquaculture a potential big money business for the United States and a chance to reduce our reliance on foreign imports, by moving the farms away from zones near the coast that harbor habitats that are more susceptible to damage from aquaculture like coral reefs (Gentry et al., 2016) and mangrove forests (Porchas & Cordova, 2012) the environmental impacts are far less than on-shore farms (Lester et al., 2018). With proper spatial planning, the offshore farms will have minimal environmental impact and a high yield of fish (Grewin, 2017) which appeals to both the conservative and liberal voters, in the sense that it is environmentally friendly and generates revenue.

With all this being said offshore aquaculture is not the only option for raising farm fed fish while reducing environmental impacts. Alternatives like recirculating aquaculture systems are either on-shore or on-land and physically separate the fish farm from the source water with a tank (Cermaq, 2012). The water is pulled from the source (typically the ocean) and circulated through the tank, when water exits the tank it passes through a filtration system that removes effluent wastes (Cermaq, 2012).  Though other problems arise from these systems like the battle for land use and the intense amount of energy needed to power these systems.

More than 40% of the world’s population lives no more than 62 miles away from the coast (Turcios & Papenbrock, 2014, p. 837) which must be planned to allow for the best use of space (Holland, 2010). In Croatia which has been praised for its successful spatial planning policy (Holland, 2010) the beautiful beaches have caused the rapid expansion of the tourism industry, taking away potential land for aquaculture farms, leading farmers to look offshore (Holland, 2010). While beaches are becoming crowded with umbrellas and aquaculture a massive area of the world is being ignored; the areas 3-200 miles off coasts. A study by the University of California-Santa Barbara found that if aquaculture were developed in only the most productive areas of the ocean, then the same amount of seafood that is currently produced annually, could be produced in an area the size of Lake Michigan (Seifert, 2017). Not only are these recirculating systems taking up useful land space, they are using an immense amount of energy to keep the operate the systems making them very costly.

Recirculating aquaculture systems have the highest energy use requirement per kilogram of fish when compared to that of other methods in the U.S. Pacific Northwest at 567 MJ/kg (Kim & Zhang, 2018, p. 2) compared to 117 MJ/kg of a conventional flow system (Kim & Zhang, 2018, p. 2). The main contributors to the energy consumption are the circulation, aeration, and filtration of the system’s water  (Badiola et al., 2018, p. 10). The aeration of the tanks typically amounts for 20% of the total energy consumption for the farm’s production cycle (Badiola et al., 2018, p. 60) whereas in an offshore aquaculture operation, no additional aeration of the water is needed because operating in deeper waters has shown to not even change the dissolved oxygen levels in the Gulf of Maine (Holmer, 2013, p. 142) due to the high volume of water naturally passing through the system. In addition to aerating the water, the water also has to be passed through multiple filter systems which takes hydraulic pressure, requiring more energy from the circulation pumps to operate during a normal backwashing cycle (which is how the filter is cleaned) a filter will use five times as much energy (Badiola et al., 2018, p. 60).

The waste that is gathered from these filters has to be either repurposed or disposed to prevent the introduction of these wastes into the water,  this again is very costly and energy intensive. Recirculating aquaculture systems reduce nutrient loading in the sediment by filtering out effluent waste, though the process is energy intensive and produces concentrated effluent waste which then must be dealt with. Because of this reason investors have only seen a 5% return on investment in recirculating aquaculture systems (Cermaq, 2012) as compared to 52% return on investment in net pen aquaculture (Cermaq, 2012). All of these factors make offshore aquaculture (a net pen system) a more cost effective and energy efficient manner of reducing the effects of nutrient loading from aquaculture.

Seafood consumption is steadily increasing not just in the United States, but globally. By 2030, ~66% of seafood will come from aquaculture production (Gewin, 2017). The United States only acquires a small fraction of its seafood from domestic production, and 50% of the seafood that is imported comes from some form of aquaculture (Knapp & Rubino, 2016, p. 214). It is clear that the reason Americans have not began establishing domestic aquaculture is not because they do not want to eat farmed fish, but because there are regulations in place that make it far too difficult to do it in the first place. The United States is ranked number 1 in potential for offshore aquaculture development (Kapetsky, Aguilar-Manjarrez, & Jeness, 2013, p. 26) and should immediately look to streamlining the permitting process for offshore aquaculture get at this opportunity.



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